Electroless palladium thin films have been successfully deposited on hydrogenated amorphous Si from a palladium-ammine bath. The d.c. magnetron reactive sputtered 18% hydrogenated amorphous silicon (a-Si:H) possessed a hydrogen passivated surface, using an activation step prior to the electroless deposition to obtain a film with good uniformity. The specially prepared hypophosphite-based dilute metal ion bath exhibited good stability at low operating temperatures of 35–50 °C. The morphology and microstructure of the Pd aggregates were characterized by scanning transmission electron microscopy (STEM) and energy dispersive x-ray spectroscopy (EDX), while the Pd aggregates and as-deposited films from the citrate and NH3/NH4Cl baths were examined by scanning electron microscopy (SEM). Marked differences in morphology and distribution of the Pd aggregates on activated a-Si:H and c-Si substrates were observed and discussed. The as-deposited films with higher coverage from the NH3/NH4Cl bath were typically more uniform and crack-free, while those from the citrate bath suffered from incorporated hydrogen, resulting in bare spots, microcracks and local a-Si film peeling. Auger Electron Spectroscopy (AES) revealed a higher amount of co-deposited phosphorus in NH3/NH4Cl bath films than citrate bath films.

A computer simulation is presented of the reduction of void volume by incident energetic ions during Ion Beam Assisted Deposition (IBAD) of thin Ge films. The objective of the work is to understand the important mechanisms of thin film densification during IBAD. The density is affected by a number of mechanisms including: absorption of recoil atoms by voids and by diffusion of residual interstitials and vacancies. Simulations of Ge deposition under Ar ion bombardment were made using the collision cascade code MARLOWE with realistic void-sizes and for beam energies up to 500 eV. MARLOWE was used to obtain void volume loss as a function of void depth, void volume, and ion energy. The fate of residual interstitials and vacancies is taken into account.

In order to model IBAD it is important to be able to model the deposition process. We describe our three-dimensional Molecular Dynamics simulations of the vapor deposition of Ni on a Ni (100) surface under low atom mobility conditions. We found the deposited film to have a packing density of about 80% of the nominal value and to contain ribbon-like voids.

The emergence of synchrotron radiation sources has greatly stimulated the use of X-ray scattering in surface science. The absence of multiple-scattering effects allows a straightforward data analysis. In addition to determining geometric structures, it is also possible with X-ray scattering to obtain information on various types of surface disorder. The large penetration depth enables the investigation of interfaces.

We report the results of our x-ray diffraction studies on epitaxial Al(111)/Si(111) films prepared by the partially ionized beam deposition technique. Significant changes were observed in intensity profiles for samples before and after annealing. In the in-plane radial scan of Al(220) peak, the shift of Bragg peak is shown due to misfit strain. A weak satellite is also observed which indicates a semicoherent interfacial structure of the annealed film with misfit dislocations. A possible picture of misfit-induced incommensurate structure of Al films is discussed.

A microscopic strain distribution across commensurate interfaces between GaAs layers grown on semi-insulating GaAs substrates was observed by means of convergent beam electron diffraction (CBED) and large angle convergent beam methods (LACBED). Strain relaxation at a specific distance from the interface was observed in these layers without formation of misfit dislocations. It was proposed that specific point defects distributed close to the interface can explain the asymmetric broadening of high-order Laue zone (HOLZ) lines in the CBED patterns.

High resolution plan view images of clean and Au deposited Si(111) surfaces are presented. Corner holes and small holes between dimers of the DAS model of the 7×7 structure were clearly resolved. In the case of the Si (111) 5×1-Au structure the 5 times period fringes did not show fine details.

Homoepitaxy on the {1ll} face of GaAs has been long known to give films with surfaces marred with macroscopic features. We have identified this problem to be tied to the surface phase regime. We have used Reflection High Energy Electron Diffraction (RHEED) to identify a phase regime wherein specular-surfaced GaAs films can be grown. We have found that it is possible to glean information regarding the macroscopic surface morphology by monitoring the variation in the RHEED specular spot intensity during growth. This has allowed in situ monitoring of the macroscopic surface morphology of a growing film in real time which has made it possible to grow specular-surfaced films reproducibly.

The surface structure of epitaxial NiSi2 films grown on Si (111) has been determined using a new method. The backscattering signals from subsequent Ni layers in the NiSi2 (111) surface are resolved.

The topology of the NiSi2 (111) surface is concluded to be bulklike, i.e., it is terminated by a Si – Ni – Si triple layer.

The adsorption of carbon monoxide on ultra-thin films of Cu, Ni and Co on Rh(100) and Mo(110) substrates has been studied using infrared reflection absorption spectroscopy (IRAS). The CO vibrational frequency on Cu/Rh(100) and Cu/Mo(110) at low Cu coverage (∼0.1 ML) shows a blue-shift relative to its gas phase stretching frequency (2143 cm−1). This blue-shift is explained as arising from CO adsorbed on well-dispersed Cu adatoms which are either slightly positively charged due to charge transfer from Cu to the substrate or self-polarized because of a strong Cu-substrate interaction. It is further shown that three-dimensional Cu clusters, well-ordered pseudomorphic two dimensional Cu islands and single Cu atoms are distinctively characterized by the CO IR peaks at 2074 cm−1, 2095 cm−1, and 2162 cm−1, respectively. In addition, it is found that IR spectra of CO adsorbed on Ni/Mo(110) show a remarkable sensitivity to surface structural phase transitions at the Ni-Mo interface.

We report the growth of boron nitride films on (001), (110), and (111) faces of silicon using the method of pulsed excimer laser ablation. The structure of the Alms grown on the (001) and (110) orientations of Si is cubic zincblende with a lattice constant of 3.619 Å. The films were found to be heteroepitaxial on silicon (001) with the cubic BN (100) axes parallel to Si (100), as characterized by x-ray diffraction and high-resolution transmission electron microscopy. In that system, we find evidence for an unusual 3:2 commensurate lattice matching. The films appear to cubic but randomly oriented on the Si (110), and no evidence for crystallinity is found for films grown on Si (111).

Spectroscopic ellipsometric (SE) measurements of GaAs (100) were carried out in an ultrahigh vacuum (UHV) chamber, without arsenic overpressure, at temperatures ranging from room temperature (RT) to ∼610°C. Surface changes induced at elevated temperatures were monitored by in-situ spectroscopic ellipsometry. The SE data clearly displayed in real time the process of desorption of the GaAs-surface-oxide overlayer at ∼580°C. In addition, changes in the near-surface region were observed before and after the oxide desorption. The near-subsurface region (top 50–100 Å) became less optically dense after being heated to 540°C or higher. For comparison, a pre-arsenic-capped molecular-beam-epitaxy (MBE)-grown GaAs surface was also studied. After the arsenic cap was evaporated off at ∼350°C, this surface remained smooth and clean as it was heated to higher temperatures.

Scanning reflection electron microscopy was used to examine step structures which form on vicinal Si(111) specimens during resistive electrical heating under ultrahigh vacuum. Heating-current-induced step bunching occurred, forming substantially linear step-bands in specific temperature regions. Small pinning points disrupted the linearity of steps. The interaction between step-bands and large pinning points resulted in the formation of macrosteps, which showed some stability against dispersal during current reversal. Ion-etched grooves influenced step orientation during current-induced step migration.

Steady state roughness of surfaces growing by molecular beam epitaxy is investigated by Monte Carlo simulations under conditions where an ion beam is also present which sputters adatoms off the surface. If the sputtering is random, it only increases the roughness. But if the sputtering probability is strongly dependent on the binding energy of an adatom within a cluster or island, the ions can have a smoothening effect. Physical arguments are given in support of the results.

We present preliminary results aimed at investigating the effects of variation in temperature on the epitaxial growth of thin films of single elements and multilayers.

In this paper we present results of a cross-sectional electron microscopy study of films in which good epitaxy has been established and then the deposition temperature has been significantly reduced (for example to 30°C from 120°C). The main objective was to study the nature of the low temperature limit of layer by layer epitaxy and the degree of roughening as a function of the deposition conditions with an emphasis on the kinetics of the process.

Ge surface segregation on Si(100) and Si(111) substrates during silicon molecular beam epitaxy is studied as a function of growth temperature. During growth, the Ge atoms are partly incorporated into the growing layer and the residuals segregate on the grown surface. The incorporation coefficient cannot be expressed in terms of a simple thermal activation process. That is, the Ge segregation phenomena increase to maxima at around 450°C for the Si(100) substrates and at around 650°C for the Si(111) substrates. Segregation decreases above these temperatures. These reverse temperature dependences enable not only good crystallinity of the heteroepitaxial layer, but also abrupt heterointerfaces. The incorporation coefficients for Si(111) are much larger than those for Si(100), which is explained by a model based on surface migration.

We use molecular-dynamics simulations to study the growth of pure Si, Si0.5Ge0.5 and pure Ge on the reconstructed (100) surface of Si. The atoms interact with one another via effective potentials of the Stillinger-Weber form with parameters adjusted such as to describe all types of triplet interactions. Motivated by recent experimental studies of molecular-beam epitaxial films,1 we examine in particular the structure of the deposits for various substrate temperatures. We also examine the relaxation of the structure resulting from high-temperature annealing. Finally, we investigate the interdiffusion of the species at the substrate-deposit interface.

A stochastic model for the MBE growth of Ge is developed based on the master equation approach with solid-on-solid restriction and quasi-chemical approximation. The surface kinetic processes included are: adsorption, evaporation and intralayer and interlayer migrations. The growth rate, the average surface roughness and the average intensity of reflection high energy electron diffraction (RHEED) (using kinematical theory of electron diffraction’ were obtained for the MBE growth of Ge with the temperature in the range 100-500°C and a typical flux of 1 Å/sec. The average surface roughness and the growth rate are found to be independent of substrate temperature below 150°C and above 400°C. In the intermediate temperature range, the growth rate increases and the surface roughness decreases with increasing temperature. The kinetic roughening temperature above which a smooth surface remains smooth, is identified from the temperature depen-dance of the average surface roughness and RHEED intensity, as 400°C. The temperature dependance of the average RHEED intensity and the kinetic roughening temperature obtained from this study compare favorably with the experimental results. At low substrate temperature, the surface migration rate is negligible irrespective of the temperature and therefore, the surface roughness and the growth rate become independent of the growth temperature. At high substrate temperatures, the surface roughness and the growth rate attain the limiting values for the flux chosen, owing to the saturation of the available sites for the interlayer migration process. Thus, these parameters become independent of the growth temperature.

The structure, morphology, and transport properties of thin films of InN grown on several cubic semiconductors has been studied as a function of substrate temperature. Films were deposited using rf-magnetron sputtering onto the (111) face of GaAs, Ge, Si and ZrO2. In general, the film structure is such that (00.1)InN parallels the (111) plane of the cubic substrate above some deposition temperature. The in-plane structural coherence duplicates the magnitude of the calculated lattice mismatch between InN and the substrate. Electrical transport properties for growth onto (111) ZrO2 were characterized by n-type carrier concentration and mobilities ranging up to 44 cm2 /Vsec. A morphology-induced decrease in electrical mobility is observed for deposition temperatures above 350°C, as shown by SEM.

Low temperature silicon selective epitaxial growth on patterned oxidized wafers is becoming crucial to ultra large scale integration (ULSI) technologies. Low temperature processes can reduce dopant redistribution via solid state diffusion so that a sharp transition region can be obtained. This paper presents material characterization of epitaxial films grown on patterned oxidized wafers by ultralow pressure chemical vapor deposition (ULPCVD) from SiH4/SiF4/H2 (≤ 10 mTorr), in which SiF4 was used to explore its capability for selective epitaxial growth. The deposition temperature is 800°C. The effects of the SiF4 addition to SiH4/H2 are discussed. Defects in epitaxial layers resulting from a high composition of the SiF4 during deposition were characterized. Results of in–situ surface cleaning using a SiF4/H2 plasma are also presented.

This paper addresses the in-situ/in-vacuo preparation of Si (100) substrates by hydrogen plasma cleaning prior to low temperature deposition of SiO2, or epitaxial growth of Si or Ge. The paper emphasizes the effectiveness of this type of substrate surface preparation following ex-situ wet-cleaning procedures that include: i) conventional RCA cleans; ii) modified RCA cleans, which incorporate exposure of the Si substrate to ozone, O3; and iii) ozone exposure, with all of these terminated by the removal of sacrificial oxides by dilute HF. We conclude: i) all ex-situ surface cleaning of Si (100) substrates leaves behind sub-monolayer oxygen and carbon surface contamination; ii) that virtually all of the carbon can be removed by exposure of the Si surface to atomic hydrogen at a temperature of <300°C; and iii) that a necessary condition for: (a) the formation of Si/SiO2 interfaces with low defect densities, Dit<l−3×1010cm−2-eV−1, and (b) the growth of epitaxial films of Si; is that the processed Si surface exhibit a 2×1 reconstruction, as detected by LEED or RHEED, following the exposure to atomic hydrogen.